1. Technical Field
The present invention relates to an electric parking brake control device which controls an electric parking brake of a vehicle.
2. Related Art
In cars, electric parking brakes tend to replace manual-type parking brakes.
In an electric parking brake, a button is manipulated to drive an actuator such as a motor, thereby operating or releasing a parking brake. Furthermore, for example, the parking brake can be automatically operated at the time of parking, or can also be automatically released at the time of a hill start. To this end, a state (“operation” or “release”) of the parking brake needs to be stored by an ECU (Electric Control Unit) or the like.
Japanese Patent Publication Laid-open Nos. 2012-66814 and 10-181579 and National Patent Publication Nos. 2008-505791 and 2002-528681 disclose devices or methods for controlling a parking brake.
According to Japanese Patent Publication Laid-open No. 2012-66814, a memory element indicating whether a parking brake is in a change-over state to operation or to release is created after manipulation of a button. When the memory element is set after failure of a control device, the parking brake is moved to a release side by a motor, and recalibration is performed. At this time, a collision of the parking brake with a stopper is detected based on consumption current of the motor, and the parking brake is moved by a predetermined amount from this position.
According to Japanese Patent Publication Laid-open No. 10-181579, when an ignition switch is in an ON state, an actuator, such as a motor, operates and generates slight breaking torque to a parking brake. A position of a piston at this time is set as an initial position. A position at which the piston is moved back from the initial position by a predetermined amount is set as a starting point. After the parking brake is operated according to instructions, the piston is moved back to the starting point and a predetermined pad clearance is obtained.
According to National Patent Publication No. 2008-505791, a sensor detects force applied to a force transmission device or a braking device and a position of an actuator such as a motor provided in the force transmission device when the parking brake is operated or released. The drive of the actuator is controlled based on a detection value and a preset value.
According to National Patent Publication No. 2002-528681, a reference position, reference coordinates, actual coordinates of the actuator are determined by a micro-switch, a Hall sensor, or a resolver, or based on motor current, at the time of operation or release of the parking brake. In addition, a motion range is determined from release end coordinates and manipulation end coordinates of the actuator. When the actual coordinates are out of the motion range, a signal is outputted.
For example, for maintenance of the electric parking brake, there is a case where a control system (ECU etc.) for the parking brake still remains mounted in a vehicle body, and a mechanical system (a brake unit, a motor, etc.) is removed from the vehicle body and then repaired or replaced. In this case, in terms of the control system, the brake state, “operation” or “release”, is stored in the ECU before the removal of the brake. On the other hand, in terms of the mechanical system, since the motor or the like is likely to be driven at the time of repair or replacement, the brake may be switched to a position different from the position in which the brake is situated before the removal of the brake, and thus the brake state may be changed. Therefore, even though the brake state, “operation” or “release”, remains stored in the control system, the mechanical system is not necessarily in the same brake state as stored after the brake is remounted in the vehicle body. When the mechanical system is situated in a state different from the brake state stored in the control system after it is remounted to the vehicle body, there is a possibility that the parking brake does not normally function, etc.